Arc furnace for reducing oxides with carbon under pressure



Aug. 22, 1933- 1.. BURGESS 1,923,076

ARC FURNACE FOR REDUCING OXIDES WITH CARBON UNDER PRESSURE Filed Jan. 16, 1932 INVENTQR ATTORNEY Patented Aug. 22, 1933 UNITED STATES ARC FURNACE FOR REDUCING OXIDES WITH CARBON UNDER PRESSURE Louis Burgess, New York, N. Y.

K Application January 16, 1932. Serial No. 587,127

4 Claims.

The invention will be fully understood from the following description read in conjunction with the drawing, in which,

Fig. 1 is a vertical section through a preferred embodiment of my invention.

Fig. 2 is a top view of the construction shown in Fig. 1.

Fig. 3 is a detailed vertical section through a part of the construction shown in Figs. 1 and 2, and

Fig. 4 is'an' enlarged detail of a part of the construction shown in Fig. 3.

The furnace referred to is an improvement upon the arc pressure furnace shown in my U. S. Patent No. 1,512,271, issued October 21, 1924. The furnace comprises a pressure retaining vessel 1, consisting of the cylindrical steel shell 2, sealed by the top closure 3 and the' bottom closure 4. The shell is adapted to carry pressures in excess of atmospheric. The excess pressure for which the shell is constructed will depend upon the particular oxide material undergoing reduction, and while a pressure of 15 pounds gage is sufficient for many purposes, with certain materials higher pressures extending to or 20 atmospheres or even higher may be required. The furnace is-of the arc type, and for convenience is shown equipped for single phase operation, the current passing between the floor 5 of the furnace and a single central electrode. The pit comprises a floor formed of a number of carbon blocks 6 laid in parallel. At least one of the blocks is in electrical communication with a busbar or cable diagrammatically indicated as '7. One end 8 of the block is cut away to form a duct 9 through which the furnace may be tapped. Preferably the block 6 is machined so that the end 10 has atrue cylindrical surface which fits snugly in the water cooled annular sleeve 11. The water jacket 12 receives cooling water through the pipe 13" which discharges through the pipe 14. The end 15 is bolted or otherwise secured to the sleeve 11 and the bracket 16 which is attached to the end 15 is bolted to the'con- 5 ductor 7. The side wall of the pit 20 is composed of carbon blocks 21 which may be laid to form a pit of circular or angular cross-section. Some suitable refractory material, such as bauxite, alumina, magnesia, or finely divided carbon is interposed between the walls and bottom of the pit and shell 2. Such material has been indicated by 22. The electrode of opposed polarity 23 is carried by the electrode-holder 23', and this is in turn carried by the tubular conductor 24 which enters the vessel 1 through the stuffing-box 25.

The stuffing-box 25 is electrically insulated from the tubular conductor 24 and in addition an insulating gasket may be provided at 26 between the cover 2'7 and the flange 28. In this case, the bolts 29 holding the flange and cover together are insulated from one or both of these members by suitable bushings and washers of fibre or similar insulating material. The details of construction of the electrode-holder 23, conductor 24 and stuffing-box 25 are in general similar to that disclosed in the prior patent hereinabove mentioned. Either manual or automatic means may be employed to adjust the height of the electrode 24 and thereby control the length and position of the arc and the amperage flowing through the furnace. Cooling water for the electrode-holder 23 is carried downwardly within the tubular conductor 24 by means of a small pipe within the conductor 24. The top of the furnace is cooled by water supplied through pipe 33 controlled by valve 34. The water flows off through the side arm 35. The improved furnace is provided with charging ports 30 and 31 in the side wall of the shell 2. These ports comprise the flanges 40 and 41 attached to the shell 2 and the doors 42 and 8 43 which may be sealed gas tight to the respective flanges. Each door is connectedto the'com-' panion flange by means of hinges such as 44 and 45, so that it may easily be swung back when, opened to the position indicated by door 43 in Fig. 2. The doors are held closed during operation of the furnace by means of dolly-bars such as 46 and turn-screws such as 50. It will of course be understood that any similar and suitable retaining device may be employed. An annular gasket such as 51 is interposed between the flange 40 and the door 42 (Fig. 4) to make a gas tight joint.

A further improvement relates to the feature by which the excess gas over that required to maintain the predetermined pressure within the furnace is relieved. This gas carries fine abrasive particles which would ordinarily abrade valve seats and render frequent replacements necessary in the pressure control valve. In the preferred apparatus, the gas is carried off from the furnace through the side arm 60, preferably provided with the water jacket 61 to which cooling water may be introduced through the pipe 62. Before valving the exit gas, Water is introduced by means of the jet 63 so that a mixture of gas and water is constantly flowing over the valve seat. This eliminates the otherwise destructive effect of the particles carried in suspension in the gas and enables'the control valve to render prolonged eflicient service. The mixture of gas and water may, of course, flow directly to the control valve 64, but a surge tank 65 is preferably interposed between the jet 63 and the valve 64. The water will in normal operation accumulate in the tank 65 up to the level 66. The excess water, together with all of the gas in excess of that necessary to hold the furnace pressure will then pass off through the valve ,64. Any temporary accumulation of water, due to completely closing the valve 64, will simply accumulate in the tank 65 until relieved. As soon as the valve 64 is opened, the accumulated water will first escape, and thereafter the excess water and gas will pass simultaneously through the valve 64. The valve 64 may of course be automatic in operation and may be set to hold any predetermined pressure.

A further improved feature is the pressure re- ,taining tapping pct '70 which isconnected to the furnace. This comprises the receiving vessel 71, preferably provided with the water jacket '72 which may be supplied with water through inlet 73 (Fig. 2). The water discharges through outlet 74. The vessel 71 is provided with a top '75, bolted to the flange '77 to form a gas tight closure. The vessel 71 carries the annular flange 80 which is connected to the flange 81 carried by the shell 2. The companion flanges 80 and 81 are suitably bolted together to form a gas tight joint. Flange 81 is integral with the water cooled annular sleeve 82 which is in turn sealed to shell 2. Provision ismade for tapping the furnace into the pot '70, and for this purpose the tapping bar 90 is provided which enters the vessel 71 through the stufiing-box 91. The bar 90 may be manipulated by means of the handle 92. The sleeve 82 and recess 9 form a duct communicating with the lower part of the pit 20 through which fluid material may flow from the pit 20 to the tapping pct '70 when the furnace is tapped.

In operating the furnace, the charge to be reduced is introduced through either or both of thecharging ports by opening the doors 42 and 43 by an operator stationed on the platform 95. Current is preferably on during this period so that cold charge will not fall in under the electrode 23 and insulate the same from the carbon block 5. When the pit 20 has been filled with charge, a piece of waste saturated with oil may be lighted and thrown into the furnace to consume any oxygen present. This precaution is only required when starting up the furnace. The doors 42 and 43 are then gasketed and made up tight by means of the turn screws 59. The gas pressure in the furnace builds up, shortly to the predetermined desired pressure and the excess gas is vented through the valve 64. With the type 0! furnaceshown in prior patent hereinabove referred to, it was necessary to drop the furnace pressure to atmospheric before tapping. It was sometimes advisable to wait a few minutes at the conclusion of a run before reducing the pressure and tapping the reduced material which would accumulate during the run in pool 93 adjacent the lower part of pit 20. This was due to the fact that the reduced material was in equilibrium with the pressure maintained during reduction and the more volatile constituents might boil out if the pressure was immediately reduced before the reduced material had cooled substan- 'tially. Cooling would take place rather slowly in the pit 20 and for this reason either a loss of volatile constituents or a delay in the operation of the furnace might be encountered. This would be relatively more serious with large size industrial furnaces. by tapping into the vessel which is under the same pressure as the furnace. The reduced material may be tapped immediately into the vessel 70 by means of the bar and when tapped will cool rapidly to a temperature at which no loss of volatile constituents can occur. As soon as the tap has been made, the pressure in the furnace may be dropped rapidlyto atmospheric. The tapping pct '70 is disconnected and a new pot is connected to the furnace. At this stage the doors 42 and 43 are again opened for recharging. It may be desirable at this point to reach in through the doors with a bar and shake down any unreduced material hanging adjacent the upper part of the pit 20. Fresh charge is then introduced, the doors resealed, and the operation repeated. The platform 95 is slightly below the level of the charging ports to facilitate inspection and charging of the furnace.

The foregoing description is for purposes of illustration, and it is therefore my intention that the invention be limited only by the appended claims or their equivalents wherein I have endeavored to claim broadly all inherent novelty.

I claim:

1. An arc pressure furnace, comprising electrodes, adapted to be adjusted at arcing distance relative to each other, a pressure retaining shell surrounding said electrodes, an educt communicating with the said shell and extending downwardly from the point of communication, means for introducing a fluid to said educt, and a valve adapted to control said educt more remote from the said shell than the said means for introducing fluid.

2. An arc pressure furnace comprising elec- The difficulty is eliminatedv trodes, adapted to be adjusted at rcing distance relative to each other, a pressure retaining shell surrounding said electrodes, an educt communicating with said shell and extending downwardly from the point of communication; means for introducing a fluid to said educt, a tank connected to said educt, an outlet,connected to said tank, and a valve adapted to control the said outlet.

3. An arc pressure furnace comprising electrodes, adapted to be adjusted at arcing distance relative to each other, a pressure retaining shell surrounding said electrodes, a pressure retaining tapping not connected to said shell, means defining a tapping duct extending from said pot to a point adjacent the arcing distance between said electrodes, and externally controllable means for breaking an opening from a point adjacent the said arcing distance to the said duct while said shell and receiving vessel are under pressure.

4. An arc pressure furnace comprising electrodes, adapted to be adjusted at arcing distance 

